Zinc selenide-based LED shows long life

When made into light-emitting diodes (LEDs), wide-gap II-VI semiconductors such as zinc selenide (ZnSe) emit light in the blue-green part of the spectrum. If it weren't for their short lifetimes, such devices could be competition for gallium nitride-based LEDs. Adding tellurium to the p layers of a ZnSe LED stabilizes the nitrogen receptor, lengthening lifetimes; also important is proper lattice spacings in the various layers of the device, leading to a tensile strain of the quantum well. Researchers at the Universität Würzburg (Würzburg, Germany) have satisfied both these needs by building an LED that includes a layer of zinc magnesium selenide telluride, a zinc cadmium selenide quantum well, and an indium phosphide substrate. In contrast to conventional II-VI diodes made on a gallium arsenide substrate with a similar density of extended defects, the new LED shows no formation of dark-line defects, resulting in a lifetime increased by three orders of magnitude. Although the first such LED died catastrophically after 150 h when a contact failed, a reduction of the current density should increase device lifetime. Lifetime estimates for the first fabricated structure (which has only moderate quality) are at least several thousand hours. Contact Wolfgang Faschinger at [email protected].